Cheapest priced copy (Dragons of Tarkir): $0.35 at Card Kingdom, near mint, their price list as of .
Hardened Berserker 
Creature — Human Berserker · 3/2 · Common · Dragons of Tarkir · #139
Whenever this creature attacks, the next spell you cast this turn costs {1} less to cast.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragons of Tarkir | 139 | Common | $0.35 | $0.49 |
| The List | DTK-139 | Common | $0.35 | — |
3 rulings from Wizards of the Coast
- 25 February 2015The ability can apply to alternative costs to cast a spell.
- 25 February 2015If there are any additional costs to cast a spell, apply those before applying Hardened Berserker and any other cost reductions.
- 25 February 2015Hardened Berserker can’t reduce the colored mana requirement of a spell you cast.